It is generally known to use sensors such as oxygen sensors, pH meters, thermocouples and the like to measure one or more chemical properties and/or physical characteristics of a test medium. Such sensors are typically constructed to produce varying electromotive forces, electrical resistance values or another measurable electrical characteristic in response to the constituent or property being measured. By way of example only, an oxygen sensor may utilize a sensing element incorporating a galvanic cell in which a measurement electrode is exposed to a test medium while a reference electrode is isolated from the medium. The difference in electromotive force between the electrodes is then correlated to the oxygen potential in the test medium. In a thermocouple, a sensing element may incorporate two wires having different alloy compositions. These wires exhibit different electrical voltage characteristics when exposed to a common temperature gradient. Thus, measuring the relative difference in voltage between the wires is used to determine temperature.
In sensing systems that utilize the transmission of electrical data, signals may be transmitted between the sensing element and one or more units providing other functions such as monitoring units, control units or the like. This transmission may be carried out across a separable electrical connector including contact pads on the sensing element and terminal contacts associated with the conductors of the sensing circuitry. High vibration and high temperature environments may have adverse effects on the integrity of the electrical connection. It is useful to utilize an electrical connector assembly that mitigates the effects of vibration, temperature or other forces.
U.S. Pat. No. 4,983,271 to Kato et al. issued Jan. 8, 1991, discloses an oxygen sensor incorporating a multi-lead electrical connection between a sensor element and lead wires. The electrical connector disclosed in U.S. Pat. No. 4,983,271 includes a plurality of sensing electrodes carried on an end of a plate type ceramic sensor element. The electrodes are in electrical communication, within the sensor element, with an equal number of conductive contact pads exposed at the planar faces at the opposite end of the sensing element.
Conductor terminal contacts attached to wire conductors are supported on a pair of ceramic carriers overlying the conductive contact pads. A surrounding metallic fitting includes outwardly extending leaf springs. The spring leafs are compressed by a surrounding caulking ring crimped about the assemblage to deform the springs. The carriers are urged toward the sensor element to urge the terminal contacts into contact with the contact pads.
In the system of Kato et al., the leaf springs bias against an inwardly deformed caulking ring surrounding the fitting and carriers such that the fitting is maintained in compressed relation against the ceramic carriers. The deformed caulking ring presses the leaf springs inwardly toward the fitting which exerts a compressive force against the carriers.
While a system such as disclosed in Kato et al. may be fully functional, the use of a caulking ring may give rise to some limitations. By way of example, in the event that components are misaligned or if the caulking ring is incorrectly located, the sensor element may be difficult to salvage once the caulking ring is crimped. Likewise, the difficulty of removing the pressed caulking ring may make parts difficult to recondition. Moreover, there is an inherent variability involved in compressing the caulking ring in place against the leaf springs.
Accordingly, an improved electrical connector, which reduces variability and which facilitates reconditioning for use in a sensor assembly is desirable.